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Tethys Simulation
This is a simulation of what one would expect to find on a terraformed Tethys, using formulas from Math And Terraforming. Please note that not even the supercomputers at NASA can provide us with a perfect simulation. The information showed here is only an approximation. Basic data *Distance from Sun: 1453.53 million km *Distance from Saturn: 0.295 million km *Diameter: 1062 km *Solar Constant: 0.0209 *Mass: 0.000103 Earths *Mean density: 0.984 kg/l *Saturn's period: 29.457 Earth years *Day length: 1.888 Earth days *Rotation axial tilt: 17 degrees to the ecliptic Atmosphere See Atmosphere Parameters Given the very low gravity, it will be difficult for Tethys to hold an atmosphere. During this simulation, we will use an atmosphere with the same pressure at sea level as Earth's and a similar composition. *Atmosphere stability for oxygen molecules: **Earth's gravity (15 degrees C): 4.116 **Tethys's gravity (15 degrees C): 117.1 **Tethys's gravity (0 degrees C): 111.0 **Tethys's gravity (-150 degrees C): 50.03 *Atmosphere stability for water molecules: **Earth's gravity (15 degrees C): 7.320 **Tethys's gravity (15 degrees C): 208.1 **Tethys's gravity (0 degrees C): 197.3 **Tethys's gravity (-150 degrees C): 88.9 *Atmosphere stability for hydrogen molecules: **Earth's gravity (15 degrees C): 65.88 **Tethys's gravity (15 degrees C): 1873 **Tethys's gravity (0 degrees C): 1776 **Tethys's gravity (-150 degrees C): 800.5 notes: A value below 10 means stability for over a million years, a value between 10 and 100 means stability between 0.1 and 10 millions of years, while a value higher then 100 means stability for less then 10 thousand years. This calculation does not include solar wind erosion. Tethys might be terraformed in a different way, with an average temperature around 0 degrees (see below). Conclusion: The atmosphere of Tethys will be divided in two distinct layers, separated by a greenhouse gas buffer. In the upper layer, where temperature will be low, oxygen and nitrogen can be held for maybe a thousand of years. However, water vapors, if they make their way that far, will be lost into space. In the lower layer, even oxygen is nearly unstable. Water vapors will fast rise to the upper layer. Hydrogen, resulting from interaction between water molecules and ionizing radiation, will escape into space very fast. The good thing is that Tethys lies in Saturn's magnetosphere and is protected from the solar wind. The atmosphere will look like this: Ground average temperature: 15 degrees C *Surface pressure at sea level: 1 *Atmosphere total mass (Earth = 1): 1.06 *Atmosphere breathable height: 546 km *Atmosphere total height: 1625 km Ground average temperature: 0 degrees C *Surface pressure at sea level: 1 *Atmosphere total mass (Earth = 1): 1.02 *Atmosphere breathable height: 538 km *Atmosphere total height: 1601 km Ground average temperature: -150 degrees C *Surface pressure at sea level: 1 *Atmosphere total mass (Earth = 1): 0.63 *Atmosphere breathable height: 393 km *Atmosphere total height: 1170 km Combined values (surface temperature = 0, above greenhouse layers temperature = -150) *Atmosphere total mass (Earth = 1): 0.89 *Atmosphere breathable height: 467 km *Atmosphere total height: 1390 km. As one can see, the atmosphere will be higher then one moon's diameter. At that distance, gravity is reduced to 1/4, causing it to further expand into space. Also, gas motion speed at that height will be close to the escape velocity. Because of this, the atmosphere of Tethys will be unstable. We need to reduce the atmosphere to a level that could resist at least for a thousand years. # Reduce surface temperature, which will decrease the speed of gas molecules # Reduce density, which will force the atmosphere to be more compact. We can reduce temperature down to water melting point (zero C). This is probably the lowest temperature which we can have if we want green plants to exist. However, a reduction from +15 to 0, will only decrease molecular speed by 5.2%. Reducing pressure will also have only limited effect. For Earth, reducing atmospheric pressure from 1 bar to 0.3 will be like taking all air out from sea level to the altitude of 8.4 km. The atmosphere will shrink with 8.4 km, from 25 to 16.6 km. In our simulation, this will remove 467 km of the atmosphere, to 923 km, a height that is still very close to one diameter. Everything will be on a very delicate balance. In order to make this atmosphere breathable, we have to change composition. It will no longer have 80% nitrogen and 20% oxygen, but 80% oxygen and 20% nitrogen. The effect is that the air will be breathable just like on Earth. Side effects will be that airplanes will fly more difficult and with less nitrogen there will be less nitrates available for plants in the soil. Temperature Main article: Temperature. The first problem with Tethys is that we need to gain the correct surface temperature. The Solar Constant is small (0.0209), compared to Earth (1.98). We will need Greenhouse Gases. The Greenhouse Calculator shows us that Tethys will need 0.656 kg/sqm of sulfur hexafluoride for a temperature of 15 degrees C and 0.585 kg per square meter for 0 degrees C. Climate Simulation Main article: Climate. On Earth, the average temperature is +15 degrees C. Technicians will try their best to keep on Tethys a surface temperature of 0 degrees C, because the atmosphere will not be stable at +15. Tethys has a smaller diameter then Earth (0.083), so air currents can mix temperatures faster. The atmosphere will be high enough to pass over all Geographic barriers. However, with a more rarefied atmosphere, some differences might appear. Average temperatures for each latitude: At equinox: *poles: -0.9 C *75 deg: -0.4 C *60 deg: -0.2 C *45 deg: 0 C *30 deg: 0.1 C *15 deg: 0.2 C *equator: 0.3 C At winter solstice: *poles: -0.9 C *75 deg: -0.7 C *60 deg: -0.4 C *45 deg: -0.2 C *30 deg: 0 C *15 deg: 0.1 C *equator: 0.2 C At summer solstice: *poles: -0.1 C *75 deg: 0.1 C *60 deg: 0.2 C *45 deg: 0.2 C *30 deg: 0.3 C *15 deg: 0.3 C *equator: 0.2 C Day - night cycle variation: Tethys has not a long day (1.888 Earth days) and is well protected by its greenhouse layer. So, temperature variations between day and night will not be significant. *Daily temperature variation: 0.06 degrees C Because day-night cycle will only bring changes of temperature below 0.1 degrees C, this can be considered negligible. Seasons: As seen above, Tethys will have small seasonal temperature changes. At the poles, differences will be of only one degree Celsius. Altitude variations: Because the atmosphere will be very fluffy, its density will not change significantly with altitude and can be considered negligible. Conclusion. Tethys will have only very small temperature variations, that will be more visible at the poles. Because the year on Saturn is very long, it might be possible for small amounts of snow to accumulate at the poles, while water will slowly melt at the equator. With so limited temperature variations, the air will tend to 100% saturation with moisture. This will cause clouds and hazes to permanently form. It might be raining or even snowing. However, because of no massive temperature variations, precipitations will be rare. With a low gravity, snow will need a long time to fall on the ground. Geography See also: Geography and Geographic Pattern - Craters. Tethys has a density a bit smaller then water. Because of this, we can speculate that it is made almost entirely of water ice, with very small amounts of other materials (dissolved gasses and only little rocks and tholins). Terraformers have 3 major ways to transform an icy Outer Planet: #Increase the heat, melt the ice and transform it into an Oceanic Planet, then leave it as it is. #If possible, build Artificial Continents after melting all the ice. #Use Ground Insulation, to save the icy crust, then cover it with solid rock. However, for Tethys, things are different. Heating will be very difficult, because if temperature exceeds a critical level, the atmosphere will lose its stability within a human lifetime. On the other hand, building a ground insulation with materials available there, will be very hard (we have nearly nothing but water). An alternative solution will be to actually increase temperature to zero and let everything as it is. On the ice, which will reach zero degrees C, microbes and some algae can grow. Snow worms can feed with this. Water will melt, but will not accumulate in large quantities. Ponds might form, but they will not have a chance to get too deep. Geographic Pattern: The moon will remain basically as it is, with large impact crater basins and some canyons. Tethys will probably be the only celestial body in the Solar System that will not change after terraforming. Conclusion: Tethys will remain as it is, with all current Geographic features. The Sky As any Outer Planet, Tethys will have a lot of moisture in its atmosphere. Because of this, fogs and clouds will be common. Probably the atmosphere will never be clean enough to see even a corner of blue sky. Still, from orbit, some celestial bodies will be visible. The Sun will appear 0.97 units wide (like an object 0.97 mm wide will appear if you look from a distance of 1 m, see Angular Size for details). Saturn and other satellites visible as disks will be: *Saturn - 395 units *Mimas - 0.82 to 3.63 units *Enceladus - 0.95 to 8.85 units *Dione - 1.67 to 13.70 units *Rhea - 1.86 to 6.58 units *Titan - 3.39 to 5.55 units *Iapetus - 0.38 to 0.45 units Some planets will also be visible: *Mercury: 4.6 to 4.8 *Venus: 1.7 to 2.0 *Earth: 2.9 to 3.4 *Mars: 5.9 to >6 *Jupiter: -0.2 to 2.4 However, people from the surface will not see this, unless they fly into outer space. Human Colonies *Population limit: 0.38 million *Land population feeding capacity: 3.3 people fed from one square km *Largest city supported by environment: 1 500 people Assuming it will have similar types of terrain Earth will have, Tethys can support a Population Limit of 380 000 people. This is comparable with a large town on Earth. Still, large communities will not be supported by the environment. Industry Tethys is almost entirely made of water ice. Whatever industrial corporations will be there, they will have to import all their primary materials. This will make production expensive. The main source of energy will be nuclear. Agriculture The low temperature does not allow farming. Also, without an ocean, there will be no fish. Settlers will have to grow their food in insulated buildings. This will be expensive. Transportation The surface can be used for building ice roads. Without iron, railways cannot exist. Air transport will be also possible, because of the small gravity. Since Tethys is tidal locked, there is no place for geosynchronous satellites. The moon has a small Hill sphere, that will be in part filled by its atmosphere. There is limited space for communication satellites. There will be constructed at least one base on the surface, for space travel. Large interplanetary ships, carrying passengers and cargo to and from Saturn, will dock at Helene. Then, smaller ships will ferry between the little moon Helene and Tethys. Tourism What will draw attention on Tethys is the fact that its surface will not be significantly transformed. this moon will be a good place to study the surface of an icy moon without wearing space suits. Wild Life The ecosystems will be very small. Bacteria, lichens and some algae will grow in and on the ice and snow. Snow worms and a few other inferior organisms can feed on them. Birds and mammals will find it difficult to adapt to this environment, where they will only find very little food. Category:Simulation Category:Math